July 4, 2014

Scientists Reformulate Their Knowledge Of Dark Matter

For decades, the mystery of Dark Matter has been at the forefront of physics research. Since the 1930s, scientists have been aware that all of the mass that we can see – the stars, the dust, the planets, and black holes – makes up only 20% of the Universe. The rest, it seems, is made of some other form of matter; something different than the protons, neutrons, and electrons that we are most familiar with.

There were many initial theories of Dark Matter proposed that all fell into three broad categories: Hot, Warm, and Cold Dark Matter. These temperature designators were actually an indication of how quickly the matter moved through space. So, for instance, neutrinos were initially proposed as a solution to the Dark Matter problem. Because of their low mass, they move at nearly the speed of light, and consequently fall into the Hot Dark Matter category.

However, Dark Matter has been observed to clump together, likely indicating a massive particle or object, suggesting that it is slow moving. As a result, most theorists have migrated over to the Cold Dark Matter camp as the most likely solution. Even within that category, though, there are still multiple solutions that are possible.

The matter is not settled however, because even the Cold Dark Matter theory has some challenges, as theory has yet to match all of the available data. But emerging research, recently published in the academic journal Nature, from the UPV/EHU's Department of Theoretical Physics and the National Taiwan University has shed some new light on this problem.

As researcher Tom Broadhurst explains: "guided by the initial simulations of the formation of galaxies in this context, we have reinterpreted cold dark matter as a Bose-Einstein condensate. The ultra-light bosons forming the condensate share the same quantum wave function, so disturbance patterns are formed on astronomic scales in the form of large-scale waves."

Consequently, this theory that the cores of some galaxy types, such as dwarf galaxies, should possess large stationary waves of Dark Matter called solitons, which would solve some of the odd observations of dwarf galaxy cores.

Their work also suggests that such galaxies would form later in the evolution of the Universe compared to other Cold Dark Matter models. This presents an opportunity for a data driven test, and the team is currently examining archival data from the Hubble Space Telescope to map the evolutionary time scales of these dwarf galaxies.

While still incomplete, the initial findings are very promising, supporting this work which suggests that Dark Matter is, in fact, a very cold quantum fluid that has driven the formation of galaxies and the structure of the Universe as a whole.